Artificial ventilation of critically ill, traumatized, or anesthetized persons is a life-saving procedure. Artificial ventilation may be performed by applying negative pressure around the chest with an “Iron Lung”, or by pumping gas at positive pressure into the airways, called “Intermittent Positive Pressure Ventilation (IPPV)”. IPPV may be applied through a tightly fitting face mask, or via a tube inserted into the trachea of the patient, called “Endotracheal Tube (ETT)”. In recent years a hybrid method, namely the “laryngeal mask”—a catheter tip pear shape inflatable occluder that fits over the glottis at the entry to the trachea—has gained popularity. In addition to negative pressure ventilation and IPPV other (alternative) modes of ventilation have been described. These include “High Frequency Ventilation (HFV)”, jet ventilation, “Constant Flow Ventilation (CFV)”, and external chest vibration with tracheal bias flow.
To achieve effective IPPV, a tight seal must be formed between the gas delivery tube, such as the ETT or a tracheotomy tube, and the patient's airway. Thus, when gas (air; oxygen) pressure in the delivery tube rises it flows into, and only into, the person's lungs to induce inhalation. When the pressure in the gas delivery system falls bellow the pressure in the lungs the flow is reversed and CO2-rich gas exits the lung. In conventional IPPV the expiratory outflow from the lung is through the same lumen of the ETT through which the gas flowed into the lung. Therefore, the lumen of the ETT must be as wide as possible to facilitate free exhalation without build-up of excessive intra-thoracic pressure.
When positive pressure ventilation is used, it is usually possible to control the respiratory rate, the volume of each breath (Tidal Volume) and the relative duration of the inspiratory and expiratory phases of each breath (I:E Ratio). It is also usually possible to control or limit the peak pressure during inspiration (PIP) and the minimal pressure at the end of expiration (PEEP). In addition, it is often desirable to facilitate self-triggering of the initiation of the breathing cycle by sensing the patient's brief drop in airway pressure induced by his/her inspiratory effort. This signal is used to actuate the delivery of a breath by the ventilator in tandem with the patient's own inspiratory effort.
While there are many models of ventilators with a variety of features and controls, all IPPV systems are only capable of ventilating the whole lung en bloc, or, at the most ventilating the two lungs with a special, two lumens ETT, using two ventilators. Current technology does not allow ventilation of lobes or segments of the lung individually, despite the substantial inhomogeneity of the disease processes encountered in most lung diseases.
German Patent 2055049 and U.S. Pat. No. 5,265,593 the contents of which are incorporated herein by reference, disclose an endotracheal tube equipped with a cuff balloon that is connected via an accessory channel to an actuating apparatus that rhythmically inflates the sleeve, while a steady flow of air or oxygen is blown through the main lumen of the tube. When the cuff baloon is inflated inside the patient's trachea it occludes the exit of air around the tube and the lungs inflates. When the cuff balloon is deflated, the lungs deflate with gas exiting around the tube, while gas is still flowing into the trachea through the tube's main channel. The lack of control over intra thoracic pressure leading to risk of lung hyperinflation and pneumothorax are major concerns with this method. The invention disclosed herewith describes an improved intra-tracheal ventilation method and tube that overcomes the deficiencies of the previous method.